Door assembly for an enclosure having a tight shielding for high frequency emissions

ABSTRACT

A door assembly having a casing member surrounding a door opening, a door mounted on the casing member for closing the opening with electrical sealing means disposed therebetween. The improvement is the provision of magnetic means for clamping the door and casing against the electrical sealing means to insure a minimum transitional resistance therebetween. In one embodiment of the invention, the magnets are electromagnets which require deenergizing to enable opening of the door. Another embodiment of the invention, the magnets are permanent magnets with associated pole pieces which are shifted relative thereto to reduce the magnitude of the magnetic force to enable opening of the door. The third embodiment of the invention, is a provision of two groups of magnets with their poles aligned with or without pole pieces interposed therebetween with the groups of magnets being moved relative to each other to enable reducing the magnetic force to enable opening the door.

United States Patent Kaiserswerth 51 Sept. 19, 1972 [54] DOOR ASSEMBLYFOR AN ENCLOSURE HAVING A TIGHT SHIELDING FOR HIGH FREQUENCY EMISSIONS[72] Inventor: Hans-Peter Kaiserswerth, Regensburg, Germany [73]Assignee: Siemens Aktiengesellschaft, Berlin I and Munich, Germany [22]Filed: March3, 1971 [21] Appl. No.: 120,469

[30] Foreign Application Priority Data March 5, l970 Germany ..P 20 105l6.2

9/1969 Beyer et a1. ..24/201 B X 8/1965 Crandelll ..292/25l.5 X 5/1949Mark et a]. ..292/25 1.5 X

[ 5 7] ABSTRACT A door assembly having a casing member surrounding adoor opening, a door mounted on the casing member for closing theopening with electrical sealing means disposed therebetween. Theimprovement is the provision of magnetic means for clamping the door andeasing against the electrical sealing means to insure a minimumtransitional resistance therebetween. In one embodiment of theinvention, the magnets are electromagnets which require deenergizing toenable opening of the door. Another embodiment of the invention, themagnets are permanent magnets with associated pole pieces which areshifted relative thereto to reduce the magnitude of the magnetic forceto enable opening of the door. The third embodiment of the invention, isa provision of two groups of magnets with their poles aligned with orwithout pole pieces interposed therebetween with the groups of magnetsbeing moved relative to each other to enable reducing the magnetic forceto enable opening the door.

11 Claims, 7 Drawing Figures PATENTEDSEP 1 9 I972 3, 91, 9 sum 1 OF 2INVENTOR ATTYS.

PATENTEUSEP 19 I972 SHEET 2 UF 2 -ATTYS.

DOOR ASSEMBLY FOR AN ENCLOSURE HAVING A TIGHT SHIELDING FOR HIGHFREQUENCY EMISSIONS BACKGROUND OF THE INVENTION 1. Field of theInvention The present invention is directed to a door assembly for anenclosure having a tight shielding for high frequency emissions.

2. Description of the Prior Art Enclosures which have a shielding forhigh frequency emissions comprising a metal foil lining on the walls ofa room are well known in the art. In such arrangements, a door assemblycomprising a door member pivotally mounted on a casing or frame member,which is connected to the shielding, and an electrical sealing membersuch as cords of metal fabric or contact springs which are providedbetween the door and frame. The door is held against the frame to insurecontact through the electrical sealing member by mechanical means toinsure a faultless electrical connection around a periphery of theopening. In many instances, due to misalignment between the door and thecasing, gaps do occur in the electrical connection which create anunhomogeneous shielding for the room due to the difference in thetransitional resistance at the electrical sealing member. To insure afaultless electrical connection around the periphery of the opening theprior art assembly uses a heavy rigid structure for the door so that themechanical clamping forces applied thereto would provide the desireduniform contact pressure on the sealing member around the periphery ofthe open- It has been suggested to utilize a shielding foilon one sideof the door which is held or pressed-by an elastically secured magneticband or strip against the casing frame. However, the magnetic forces ofthe magnetic band is very small and the foil does not have a spring likecharacteristic to provide a self-cleaning feature and may developimperfect electrical connections. Since the attraction of the magneticbands is so slight that it will not twist the door to correct anymisalignment therebetween, both the door and frame must be mechanicallyrigid and very accurately adjusted for alignment to insure equallyapplied force between the door and frame. The proposed magnetic systemof the fixedly mounted on the door and easing member with their poles inalignment for attraction and with pole pieces interdisposed therebetweenwhich are movable relative to the groups of magnets to increase anddecrease the magnetic force clamping the door against the casing member.

Accordingly, an object of the present invention is to provide animproved door assembly for an enclosure having a tight shielding forhigh frequency emissions.

Another object of the present invention is to provide a door assemblyfor an enclosure having tight shielding prior art have such a weakmagnetic force that the door SUMMARY OFTHE INVENTION The presentinvention is directed to an improved door assembly in which magnets aredisposed around a periphery of the door opening in the casing member topull the door member against the casing member with sufficient force totwist the door member if necessary to apply an equal contact pressurearound the opening between the members and with such sufficient forcethat the door cannot be opened by hand. In one embodiment of theinvention, electromagnets are distributed about the opening of thecasing and must be deenergized to enable the door to be opened. In asecond embodiment of the invention, permanent magnets with a pole piecefor each magnet are distributed around the opening of the door withrelative movements between the pole pieces and the associated poles forhigh frequency emissions which assembly utilizes magnetic forces toclamp the door against the casing with twisting if necessary tocompensate for misalignment therebetween.

A still further object of the present invention is to provide a doorassembly for an enclosure having tight shielding for high frequencyemissions in which the door can be of a thinner and less rigidstructure.

Yet another object of the present invention is to provide a doorassembly for an enclosure having a tight shielding for high frequencyemission utilizing magnetic force from permanent magnets for clampingthe door tightly against the casing which force is adjustable to enableopening of the door.

Other objects, features and advantages of the invention .will be readilyapparent from the following description of the preferred embodimentsthereof taken in conjunction with the accompanying drawings althoughvariations and modifications may be effected without departing from thespirit and scope of the novel concepts of this disclosure.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a side elevational view ofthe door assembly of the prior art;

FIG. 2 is a cross sectional view taken on lines ll-II of FIG. 1;

FIG. 3 is a side elevational view of the door assembly of the presentinvention;

FIG. 4 is a cross-sectional view taken on lines IVIV of FIG. 3;

FIG. 5 is a side elevational view with portions of the door removed forpurposes of illustration of an embodiment of the door assembly of thepresent invention;

FIG. 6 is a cross sectional view of another embodiment of the doorassembly of the present invention illustrating the positioning of thepermanent magnets in a clamping position; and

FIG. 7 is a view similar to FIG. 6 illustrating the.

placement of the permanent magnets in an unclamping position.

DESCRIPTION OF THE PREFERRED EMBODIMENT A prior art door assembly forenclosures such as rooms having tight shielding for high frequencyemissions is illustrated in FIGS. 1 and 2 and includes a door member 1and a frame or casing member 2. The casing member 2 has portions such astubular pieces joined together such as by welded joints in a rectangulararrangement to define a door opening which is closed by the doormember 1. To insure an electrical connection between the door member 1and casing member 2, electrical sealing means 3 such as contact springsor a metal fabric cord is placed on either of the members 1 or 2 tosurround the opening and to be pressed between the casing member 2 and acontact surface 4 of the door member 1 as the door member is clamped inthe closed position illustrated. The door member 1 is mounted on thecasing member 2 by a pair of hinge members 6 and is clamped in theclosed position by a mechanically actuated latching mechanism havingthrust bars 5.

The assembly was utilized in a shielded enclosure such as a room havinga shielding formed by a nonmagnetic metal foil 7 such as copper, whichfoil is electrically connected to the casing member 2 or to a foilprovided on the casing member 2. The door member 1 could have a similarfoil provided on its contact surface 4 to provide the desired shieldingcharacteristics for the door assembly.

Since the clamping force was provided by the thrust rods or pins 5, thedoor member 1 in the prior art device illustrated in FIGS. 1 and 2 wasof a heavy, rigid structure to prevent twisting and to apply theclamping force equally around the periphery of the opening in the casingmember 2. If the door member 1 was not perfectly aligned with the casingmember 2, either due to imperfections in the structure of the doormember 1 or the casing member 2 or the hinge members 6 whichimperfections cause a misalignment, the door could not twist to insurean equal contact pressure applied to the sealing members 3 disposedbetween the door I and easing 2. Furthermore, if the clamping mechanismwere misaligned, the door would not twist to compensate for unequalapplication forced by the clamping members such as the thrust rods toprovide the equal clamping pressure on the sealing means 3.

In the present invention, as illustrated in FIG. 3, the door assemblycomprises the door member 1', the frame member 2 with electrical contactsealing means 3 disposed therebetween. The door member 1 is mounted onthe casing 2 by means of hinges 6' which as illustrated in FIG. 3 are ofdouble pivotal type which are commercially available.

To provide a clamping force, magnets 8 are equally distributed aroundthe periphery of the opening and as illustrated on the casing member 2to apply a force to the edge of the door member 1' or to an areaadjacent thereto. The magnets 8 are distributed in a manner to apply aclamping force to all edges of the door around the periphery of theopening in the casing member 2 to pull the door against the sealingmeans 3 to insure a faultless and gapless electrical connection betweenthe casing member 2 and an inner surface 4' of the door member I. Theforce of the magnets 8 is of a high magnitude so that misalignmentsbetween the door 1 and the casing member 2 are corrected by twisting thedoor 1 which as illustrated is substantially thinner and less rigid thanthe door of the previously known prior art devices. The magnetic forceof the magnets 8 has a high magnitude such that the door 1' cannot beopened by hand using a handle 9 provided thereon without first reducingthe magnetic force. The magnetic force is also of such a high magnitudethat it prevents accidental opening of the door without performing thestep of deenergizing or changing the magnetic force clamping the door 1against the electrical sealing means 3.

In one embodiment of the invention, the magnets 8 are electromagnetshaving conventional electrical circuits. To open the door, a switch (notillustrated) is provided to deenergize the electrical circuit of theelectromagnets to allow the opening of the door. It is preferable thatthe switch is disposed on the outside of the shielded space and thatmechanical linkages such as a plastic rod movable in a shielded tubeactuates the switch from the inside of the shielded room or enclosure.

As illustrated in FIG. 5, another door assembly of the present inventionis illustrated. Preferably the change is that the magnets 8' which arepreferably electromagnets have a larger surface area for providing themagnetic force to draw a door member (not illustrated) tightly againstthe leaf-type contact springs of the electrical connecting means 3.

Another embodiment of the present invention utilizes permanent magnetssuch as the magnet 12 in FIG. 6 which are disposed on either the casingmember or door member around the periphery of the door opening. Thepermanent magnets 12 have sufficient force to prevent the accidentalopening of the door 1' or the opening of the door 1' without firstdecreasing their magnetic force.

In an embodiment of the invention, the permanent magnets are mounted ina plastic member or sheet 14 and have pole pieces 13 of a magneticmaterial such as soft iron associated with each of the poles of themagnets and carried in a nonmagnetic plastic member or sheet 15. Members14 and 15 are mounted on either the casing member 2 or the door member1' and are relatively movable to each other so that if the member 14supporting the permanent magnets 12 is shifted in the direction of thearrow of FIG. 6, the poles of the magnets 12 will be shifted from theirpole pieces 13 to an area of the nonmagnetic plastic material 15 todecrease the magnetic force applied for holding the door member in theclamped position on the casing member 2. In a similar manner, theplastic or non-magnetic material of the sheet 14 supporting thepermanent magnets 12 can be rigidly mounted to the casing member or thedoor member and the non-magnetic plastic sheet 15 supporting the polepieces 13 moved with respect to the magnets 12.

In another embodiment, two groups of magnets 12 each carried in anonmagnetic support sheet 14 are mounted on both the casing member andthe door member with the poles of the magnets 12 arranged with the Northpole of one group coacting with the South pole of the other group to bein an attracting condition. By relatively moving the two groups ofmagnets, as illustrated in FIG. 7 so that like poles are in alignmentwith like poles, the magnets are opposing each other enabling opening orunclamping of the door. Either group of magnets can be shifted to enableopening of the door from either the inside or the outside of theenclosure. Preferably, a thin foil 7 of non-magnetic material such ascopper is sandwiched between the groups of magnets.

Preferably, pole pieces such as 13 carried in a nonmagnetic supportsheet or member are utilized with the two groups of the magnets 12 asillustrated in FIG. 6. The pole pieces 13 can be immovably attached tothe casing member and the door member with a thin nonmagnetic foil 7disposed therebetween. Either of the groups of magnets 12 are movable toshift the magnets 12 from the position for clamping as illustrated inFIG. 6 to a non-clamping position as illustrated in FIG. 7. Anothervariation of utilizing the two groups of magnets as illustrated in FIG.6 is the permanently mounting of the nonmagnetic carrier 14 for themagnets 12 to both the door member and the casing member and slidablymoving the nonmagnetic carriers 15 for the pole pieces 13 from aposition illustrated with the pole pieces in alignment with the poles ofthe two groups of magnets to a position in which the nonmagneticmaterial of the member 15 are between the poles of the magnets 12 toreduce the effective magnetic force and enable the opening of the door.

The relative movement of the magnets with respect to the pole pieces orwith respect to each other discussed hereinabove provides means forreducing the magnetic force applied to clamp the door member 1 onto thecasing member 2. Thus, the means for unclamping can be obtained byshifting either the magnets relative to their pole pieces if just asingle group of magnets and pole piece units are utilized or shifting agroup of magnets relative to the second group of magnets if two groupsof magnets are utilized, or finally by either shifting the pole piecesfor the two groups of magnets relative to the magnets or shifting thetwo groups of magnets to change the relationship of the poles of themagnets from an attracting to a repelling alignment.

Although various minor modifications might be suggested by those versedin the art, it should be understood that I wish to employ within thescope of the patent warranted hereon all such embodiments as reasonablyand properly come within the scope of my contribution to the art.

I claim as my invention:

1. In a door assembly for use in an enclosure such as a room which hasmeans to provide a tight shielding for a high frequency emission, saiddoor assembly having a casing member composed of portions arranged todefine a door opening, a door member mounted on the casing member formovement between a first position closing the door opening and a secondposition enabling access through the door opening, sealing meansdisposed between the members around the opening to provide an electricalconnection therebetween when the door is in the first position, andmagnets distributed around the opening to pull the door member againstthe casing member to insure an electrical connection between the sealingmeans and the members the improvement comprising the sealing means beingself-cleaning contact springs separated 6 and spaced from the magnets sothat the magnetic force of the magnets IS free from interference fromthe material of the sealing means, and the door member being a thin andtwistable structure so that the magnets pull the door member against thecasing member-to apply a clamping force to the contact springs to insurea shielding connection free of gaps and with a minimum transitionalelectrical resistance therebetween.

2. In a door assembly according to claim 1, which includes means forchanging the magnetic forces clamping the door member against the casingmember to enable moving the door from the first to the second position.

3. In a door assembly according to claim 2, wherein the magnets areelectromagnets.

4. In a door assembly according to claim 2, wherein the magnets arepermanent magnets, with a pole piece associated with each of thepermanent magnets, and the means for changing the magnetic forceincludes means for relatively moving the magnets and their respectivepole pieces into and out of alignment.

5. In a door assembly according to claim 2, wherein the magnets arepermanent magnets arranged in two groups with the one group mounted onthe door member and the other group mounted on the casing member, saidgroups of magnets being arranged with the magnetic poles in anattracting alignment with pole pieces disposed between the poles of thetwo groups of magnets, and said means for changing the magnetic forceincluding means for relatively shifting the pole pieces from a positionin alignment with the poles of the two groups of magnets to a positionout of alignment therewith to change the magnetic forces therebetween.

6. In a door assembly according to claim 5 further including anonmagnetic sheet metal foil disposed between the pole pieces and one ofthe groups of magnets.

7. In a door assembly according to claim 2, wherein the magnets arearranged in two groups of permanent magnets with one group being mountedon the casing member and the other group being mounted on the doormember, said means for changing the magnetic force comprising means tomove one group of magnets relative to the other group to shift the polesof the magnets between attracting and repelling relationship.

8. In a door assembly according to claim 7 which includes a non-magneticsheet of metal foil disposed between the two groups of magnets.

9. In a door assembly according to claim 7, which further includes polepieces for each of the poles of the two groups of magnets, said polepieces being fixedly mounted on one of the members to intensify themagnetic force between the two groups of permanent magnets.

10. In a door assembly according to claim 9, wherein a non-magneticsheet metal foil is disposed between one group of magnet and the polepieces.

11. In a door assembly according to claim 7, which further include a setof pole pieces immovably attached on each of the members between thegroups of permanent magnets, and a non-magnetic foil disposed betweenthe sets of pole pieces.

1. In a door assembly for use in an enclosure such as a room which hasmeans to provide a tight shielding for a high frequency emission, saiddoor assembly having a casing member composed of portions arranged todefine a door opening, a door member mounted on the casing member formovement between a first position closing the door opening and a secondposition enabling access through the door opening, sealing meansdisposed between the members around the opening to provide an electricalconnection therebetween when the door is in the first position, andmagnets distributed around the opening to pull the door member againstthe casing member to insure an electrical connection between the sealingmeans and the members the improvement comprising the sealing means beingself-cleaning contact springs separated and spaced from the magnets sothat the magnetic force of the magnets is free from interference fromthe material of the sealing means, and the door member being a thin andtwistable structure so that the magnets pull the door member against thecasing member to apply a clamping force to the contact springs to insurea shielding connection free of gaps and with a minimum transitionalelectrical resistance therebetween.
 2. In a door assembly according toclaim 1, which includes means for changing the magnetic forces clampingthe door member against the casing member to enable moving the door fromthe first to the second position.
 3. In a door assembly according toclaim 2, wherein the magnets are electromagnets.
 4. In a door assemblyaccording to claim 2, wherein the magnets are permanent magnets, with apole piece associated with each of the permanent magnets, and the meansfor changing the magnetic force includes means for relatively moving themagnets and their respective pole pieces into and out of alignment. 5.In a door assembly according to claim 2, wherein the magnets arepermanent magnets arranged in two groups with the one group mounted onthe door member and the other group mounted on the casing member, saidgroups of magnets being arranged with the magnetic poles in anattracting alignment with pole pieces disposed between the poles of thetwo groups of magnets, and said means for changing the magnetic forceincluding means for relatively shifting the pole pieces from a positionin alignment with the poles of the two groups of magnets to a positionout of alignment therewith to change the magnetic forces therebetween.6. In a door assembly according to claim 5 further including anon-magnetic sheet metal foil disposed between the pole pieces and oneof the groups of magnets.
 7. In a door assembly according to claim 2,wherein the magnets are arranged in two groups of permanent magnets withone group being mounted on the casing member and the other group beingmounted on the door member, said means for changing the magnetic forcecomprising means to move one group of magnets relative to the othergroup to shift the poles of the magnets between attracting and repellingrelationship.
 8. In a door assembly according to claim 7 which includesa non-magnetic sheet of metal foil disposed between the two groups ofmagnets.
 9. In a door assembly according to claim 7, which furtherincludes Pole pieces for each of the poles of the two groups of magnets,said pole pieces being fixedly mounted on one of the members tointensify the magnetic force between the two groups of permanentmagnets.
 10. In a door assembly according to claim 9, wherein anon-magnetic sheet metal foil is disposed between one group of magnetand the pole pieces.
 11. In a door assembly according to claim 7, whichfurther include a set of pole pieces immovably attached on each of themembers between the groups of permanent magnets, and a non-magnetic foildisposed between the sets of pole pieces.